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Member Since 04 Oct 2011
Online Last Active Today, 11:43 AM

Topics I've Started

Calculating Firing Costs With External Digital Controller

15 January 2014 - 04:52 PM

Here's something I just figured out today. Seems obvious now that I realize it, but had never thought of it before:


I'm firing my little 1 cubic foot manual test kiln with some fusion buttons for my glaze formulation students. I just recently hooked it up an external Orton digital controller I got from a customer. For those of you who haven't used one, the way external controllers work is the kiln plugs into the controller unit via its regular power cord, and the controller sends power through the cord as needed to heat up the kiln. It cycles the kiln on and off like any digital controller, to control the rate of climb.


The kiln itself has a Sitter on it with a timer. You have to put a cone in the sitter that's higher than the projected firing (or just jam a piece of kiln shelf in it), push the power button, and turn all the knobs on high. Because power is only going through the sitter intermittently, as the relays in the digital control unit cycle the power on and off, the timer on the sitter only moves when there is power to the kiln. So at the end of a firing I can tell exactly how long the kiln was 'on', and calculate the cost of the firing by way of the wattage of the kiln. Awesome!

How's The Weather?

02 January 2014 - 02:35 PM

Looks like we scored 16-18 inches of snow in the last 48 hours. Blue skies finally showing through. How's your weather?

Cones And Soaking Times Theory

08 November 2013 - 10:15 AM

Nearly every day on this forum someone, often me, refers to cones and their importance in the ceramic firing process. I understand how cones work. I explain it to my students all the time. But this week I found myself with a question about cones I've never encountered before.


When it comes to soaking (holding temperature) in order to achieve heat work, we always tell people to test it with actual cones. I've heard anywhere from 15 minutes to 1 hour of soaking is necessary in order to gain one cone. There's no consistency to the system.


Here's my recent experience that has me somewhat baffled: I used to fire to cone 8 in oxidation (electric). In order to increase the life of my elements a bit, I would fire to cone 6 with a 40 minute hold to reach cone 8. Now I fire to cone 6, and I finally tested the hold time to see how long it would take me to get from cone 4 to cone 6, and it came out to 75 minutes, almost twice as long as from cone 6 to cone 8!


The at a rate of climb of 108F/hr, which is what my firings use, the difference between cone 6 and cone 8 is only 48 degrees. The difference between cone 4 and cone 6 is 108 degrees. So can we assume that the greater the temperature gap, the longer the soak time in order to achieve the heat work? Those of you who soak for cones, what cones are you using, and how long is your soak time?

Soda Kiln Build

04 October 2013 - 12:45 PM

Since it's been a pretty slow week here on the forum, I thought I'd post some eye candy to keep you all busy. On my blog HERE you can see photos of the soda kiln Doug Jeppesen and I built a couple of weekends ago at Lillstreet Art Center in Chicago. We knocked it out in about 30 hours over 3 days, from scratch. The interior of the kiln is all hard brick, with soft brick used wherever possible on the exterior.


Doug and I had built the previous kiln, too, which lasted 3 1/2 years, and new record at Lill. They tend to go through soda kilns pretty quickly. When we started on the previous version, we found that the kiln was supported on a metal framework that attempted to level the kiln since the concrete floor was really out of whack. The frame was not ideal, but due to time constraints we had to use it. This time, since we knew what we were getting into, we made them toss the frame and pour a level concrete slab. This should be their longest lasting soda kiln yet. The first firing is this weekend.